1. Field of the Invention
The present invention relates to an apparatus for transporting a recording medium in an electrographic printing or copying device.
2. Description of the Related Art
In printing and copying devices, the recording medium is transported along a printing station and printed there. The recording medium consists of paper, plastic foil material or other materials according to need. In the transfer printing station of such devices, the recording medium is printed over a defined width.
According to the embodiment of the printing device, Leporello paper, rolled products with perforations or rolled products without perforations can be printed. All types of paper are used for printing. In many instances, what is known as Leporello paper with lateral perforations is used. The transport and guiding therein ensues with driven tractor wheels which engage in the lateral transport holes of the paper. However, rolled papers without perforation are increasingly being used, these necessitating a tractorless drive mechanism.
Published PCT Patent Application No. WO-95/19929 teaches a printer which can process rolled paper both with and without perforations. The drive is therein accomplished by a tractorless friction drive. A first feed edge which prescribes the lateral position of the paper is provided in this device for exact guidance of the paper. Stabilization rollers, a vacuum brake and a roller arrangement with a loop draw are further provided in the device.
Additional measures have proven necessary for a precise, tractorless transport, particularly when relatively light recording media, or paper types, are to be transported.
Furthermore, in drive assemblies in printers it is occasionally necessary to stop the paper transport. In the continuation of the printing process, it is then required that the position of the recording medium is held, or located again with optimal precision. A particular demand arises if the drive mechanism must be swivelled away from the transfer printing station for service purposes, e.g. given breakage of the wire of the corona device located at the transfer printing station. A print job often must be restarted in such a case; i.e., pages which were already printed must be reprinted. Superfluous or duplicate pages thus are printed which must be disposed of (resulting in what is known as spoilage).